Method for restoring activity to a spent hydroprocessing catalyst, a spent hydroprocessing catalyst having restored catalytic activity, and a hyrdoprocessing process

ABSTRACT

A regenerated spent hydroprocessing catalyst treated with a chelating agent and having incorporated therein a polar additive.

This application claims the benefit of U.S. Provisional Application No.61/373,464 filed Aug. 13, 2010, the entire disclosure of which is herebyincorporated by reference.

This invention relates to a method of restoring catalytic activity to aspent hydroprocessing catalyst, the resulting hydroprocessing catalystand its use in the hydroprocessing of hydrocarbon feedstocks.

When a catalyst composition is used in the hydroprocessing ofhydrocarbon feedstocks it will tend to lose catalytic activity overtime. One of the causes of this lost catalytic activity is from thedeposition of carbon or sulfur, or both, upon the surface and in thepores of the catalyst during its use which results in the catalystactivity declining over time as feedstock is passed over the catalyst.At some point in the use of the catalyst its activity will decline to alevel at which the catalyst is considered to be spent in that its use isno longer economical relative to fresh catalyst or for other reasons.

There is disclosed in the art various methods of restoring lostcatalytic activity to a spent catalyst. One of these methods is to burnthe carbon and sulfur that is deposited upon the spent catalyst in orderto provide for the restoration of at least some of the activity to thecatalyst and to give a regenerated catalyst. The regenerated catalyst,however, typically does not have a restored activity that is as good asor approaches that of a fresh catalyst.

The prior art teaches a number of different approaches to restoringactivity to spent catalyst. For instance, in U.S. Pat. No. 7,696,120 isdisclosed a method of restoring catalytic activity to a spenthydroprocessing catalyst. In this method, at least some of the carbonthat is deposited on a spent hydroprocessing catalyst is removed in acarbon removal step with the resulting regenerated catalyst, having areduced concentration of carbon, next being subjected to a chelationtreatment to provide a revitalized catalyst with a significant portionof the lost activity being restored. U.S. Pat. No. 7,696,120 isincorporated herein by reference.

While the prior art teaches a number of useful methods for restoringcatalytic activity to spent hydroprocessing catalysts there is still anongoing need to find improved or alternative methods for restoringactivity to hydroprocessing catalysts that have become spent due totheir use in the hydroprocessing of hydrocarbon feedstocks.

Accordingly, provided is a method for restoring catalytic activity to aspent hydroprocessing catalyst to provide an additive impregnatedcomposition, wherein the method comprises: regenerating the spenthydroprocessing catalyst to remove at least a portion of the carbontherefrom to provide a regenerated hydroprocessing catalyst; treatingthe regenerated hydroprocessing catalyst with a chelating agent byincorporating the chelating agent into the regenerated hydroprocessingcatalyst to thereby provide a chelant treated regeneratedhydroprocessing catalyst; drying the chelant treated regeneratedhydroprocessing catalyst to provide a dried chelant treated regeneratedhydroprocessing catalyst having a volatiles content in the range of from0.5 to 25 wt % LOI; and incorporating a polar additive into the driedchelant treated regenerated hydroprocessing catalyst to thereby providethe additive impregnated composition.

Further provided is a hydroprocessing catalyst composition thatcomprises a regenerated hydroprocessing catalyst, a chelating agent anda polar additive. This hydroprocessing catalyst composition can be usedby contacting it under hydroprocessing reaction conditions with ahydrocarbon feedstock.

FIG. 1 presents a plot showing the hydrodesulfurization activity of acomparative catalyst versus the activity of a composition derived froman embodiment of the inventive method of regeneration and treatment of acatalyst that has become spent as a result of its use.

The invention relates to a method of restoring catalytic activity to ahydroprocessing catalyst that has become spent due to its use. Thehydroprocessing catalyst that becomes spent as a result of its useincludes any hydroprocessing catalyst known to those skilled in the artand are typically catalyst compositions that comprise a metal componenton a support material. The metal component can include a Group VIB metalcomponent or a Group VIII metal component, or both metal components. Itis preferred for the hydroprocessing catalyst to comprise both a GroupVIB metal component and a Group VIII metal component. Thehydroprocessing catalyst can also include a promoter such as aphosphorous component.

The Group VIII metal component of the hydroprocessing catalystcomposition are those Group VIII metal or metal compounds that, incombination with the other components of the catalyst composition,suitably provide a hydroprocessing catalyst. The Group VIII metal can beselected from the group consisting of nickel, cobalt, palladium andplatinum. Preferably, the Group VIII metal is either nickel or cobaltand, most preferably, the Group VIII metal is cobalt.

The Group VIII metal component contained in the hydroprocessing catalystcomposition can be in the elemental form or in the form of a metalcompound, such as, for example, oxides, sulfides and the like. Theamount of Group VIII metal in the hydroprocessing catalyst compositioncan be in the range of from about 0.1 about 6 weight percent elementalmetal based on the total weight of the hydroprocessing catalystcomposition. Preferably, the concentration of Group VIII metal in thehydroprocessing catalyst composition is in the range of from 0.3 weight% to 5 weight %, and, most preferably, the concentration is in the rangeof from 0.5 weight % to 4 weight %.

The Group VIB metal component of the hydroprocessing catalystcomposition are those Group VIB metal or metal compounds that, incombination with the other elements of the hydroprocessing catalystcomposition, suitably provide a hydroprocessing catalyst. The Group VIBmetal can be selected from the group consisting of chromium, molybdenumand tungsten. The preferred Group VIB metal is either molybdenum orchromium and, most preferred, it is molybdenum.

The Group VIB metal component contained in the hydroprocessing catalystcomposition can be in the elemental form or in the form of a metalcompound, such as, for example, oxides, sulfides and the like. Theamount of Group VIB metal in the hydroprocessing catalyst compositioncan be in the range of from about 5 to about 25 weight percent elementalmetal based on the total weight of the hydroprocessing catalystcomposition. Preferably, the concentration of Group VIB metal in thehydroprocessing catalyst composition is in the range of from 6 weight %to 22 weight %, and, most preferably, the concentration is in the rangeof from 7 weight % to 20 weight %.

The support material of the hydroprocessing catalyst can be any materialthat suitably provides a support for the metal hydrogenation componentsof the hydroprocessing catalyst including porous refractory oxides.Examples of possible suitable porous refractory oxides include silica,magnesia, silica-titania, zirconia, silica-zirconia, titania,titania-alumina, zirconia-alumina, silica-titania, alumina,silica-alumina, and alumino-silicate. The alumina can be of variousforms, such as, alpha alumina, beta alumina, gamma alumina, deltaalumina, eta alumina, theta alumina, boehmite, or mixtures thereof. Thepreferred porous refractory oxide is amorphous alumina. Among theavailable amorphous aluminas, gamma alumina is most preferred.

The porous refractory oxide generally has an average pore diameter inthe range of from about 50 Angstroms to about 200 Angstroms, preferably,from 70 Angstroms to 175 Angstroms, and, most preferably, from 80Angstroms to 150 Angstroms. The total pore volume of the porousrefractory oxide, as measured by standard mercury porisimetry methods,is in the range of from about 0.2 cc/gram to about 2 cc/gram.Preferably, the pore volume is in the range of from 0.3 cc/gram to 1.5cc/gram, and, most preferably, from 0.4 cc/gram to 1 cc/gram. Thesurface area of the porous refractory oxide, as measured by the B.E.T.method, generally exceeds about 100 m²/gram, and it is typically in therange of from about 100 to about 400 m²/gram.

As earlier noted, the hydroprocessing catalyst becomes a spenthydroprocessing catalyst by its use. The hydroprocessing catalyst can beused in the hydrotreatment of a hydrocarbon feedstock under suitablehydrotreatment process conditions. Typical hydrocarbon feedstocks caninclude petroleum-derived oils, for example, atmospheric distillates,vacuum distillates, cracked distillates, raffinates, hydrotreated oils,deasphalted oils, and any other hydrocarbon that can be subject tohydrotreatment. More typically, the hydrocarbon feedstock that istreated with the hydroprocessing catalyst is a petroleum distillate suchas a straight run distillate or a cracked distillate with thehydrotreatment being to remove sulfur from sulfur-containing compoundsor nitrogen from nitrogen-containing compounds, or both, from thehydrocarbon feedstock.

More specifically, the hydrocarbon feedstock can include such streams asnaphtha, which typically contains hydrocarbons boiling in the range offrom 100° C. (212° F.) to 160° C. (320° F.), kerosene, which typicallycontains hydrocarbons boiling in the range of from 150° C. (302° F.) to230° C. (446° F.), light gas oil, which typically contains hydrocarbonsboiling in the range of from 230° C. (446° F.) to 350° C. (662° F.), andeven heavy gas oils containing hydrocarbons boiling in the range of from350° C. (662° F.) to 430° C. (806° F.)

The hydrotreating conditions to which the hydroprocessing catalyst issubjected are not critical and are selected as is required taking intoaccount such factors as the type of hydrocarbon feedstock that istreated and the amounts of sulfur and nitrogen contaminants contained inthe hydrocarbon feedstock. Generally, the hydrocarbon feedstock iscontacted with the hydroprocessing catalyst in the presence of hydrogenunder hydrotreatment conditions such as a hydrotreating contactingtemperature generally in the range of from about 150° C. (302° F.) toabout 538° C. (1000° F.), preferably from 200° C. (392° F.) to 450° C.(842° F.) and most preferably from 250° C. (482° F.) to 425° C. (797°F.).

The hydrotreating total contacting pressure is generally in the range offrom about 500 psia to about 6,000 psia, which includes a hydrogenpartial pressure in the range of from about 500 psia to about 3,000psia, a hydrogen addition rate per volume of hydrocarbon feedstock inthe range of from about 500 SCFB to about 10,000 SCFB, and ahydrotreating liquid hourly space velocity (LHSV) in the range of fromabout 0.2 hr⁻¹ to 5 hr⁻¹. The preferred hydrotreating total contactingpressure is in the range of from 500 psia to 2,500 psia, mostpreferably, from 500 psia to 2,000 psia, with a preferred hydrogenpartial pressure of from 800 psia to 2,000 psia, and most preferred,from 1,000 psia to 1,800 psia. The LHSV is preferably in the range offrom 0.2 hr-1 to 4 hr-1, and, most preferably, from 0.2 to 3 hr-1. Thehydrogen addition rate is preferably in the range of from 600 SCFB to8,000 SCFB, and, more preferably, from 700 SCFB to 6,000 SCFB.

The hydroprocessing catalyst can become spent by it use underhydrotreatment conditions as described above. As noted, it is generallyconsidered that one cause of the loss of catalytic activity is due tothe deposition of carbonaceous material onto or into the pore structureof the hydroprocessing catalyst as a result of its use.

A spent hydroprocessing catalyst can have a carbon content generallyabove 0.5 weight percent (wt. %), with the weight percent being based onthe total weight of the spent hydroprocessing catalyst including carbonand other components deposited upon the hydroprocessing catalyst.Typically, it is considered that for a hydroprocessing catalyst to bespent the carbon content of the spent hydroprocessing catalyst is in therange of from 1 weight percent to 25 weight percent. More typically,however, the carbon content of the spent hydroprocessing catalyst is inthe range of from 2 weight percent to 23 weight percent, and, mosttypically, the carbon content is in the range of from 3 wt. % to 21 wt.%, or from 5 wt. % to 20 wt. %, or even from 6 wt. % to 18 wt. %.

In the inventive method and preparation of the inventive catalystcomposition the spent hydroprocessing catalyst is regenerated to removeat least a portion of the carbon that is deposited thereon to provide aregenerated hydroprocessing catalyst.

Any suitable method know in the art can be used to regenerate or reducethe carbon concentration on the spent hydroprocessing catalyst tothereby provide the regenerated hydroprocessing catalyst, but apreferred method includes heat treating the spent hydroprocessingcatalyst by contacting it with an oxygen-containing gas, comprisingoxygen, under suitable carbon burning conditions and in a controlledmanner so as to combust or burn or oxidize the carbon that is on thespent hydroprocessing catalyst and so as to provide a regeneratedhydroprocessing catalyst having a reduced carbon concentration that isless than the carbon concentration on the spent hydroprocessingcatalyst.

The required carbon burning conditions can be dependent upon the amountof carbon on the spent hydroprocessing catalyst and other factors, but,generally, the spent hydroprocessing catalyst is contacted with theoxygen-containing gas under regeneration conditions wherein theregeneration temperature is in the range of from 200° C. to 600° C. witha suitable heat treatment, or carbon burning, temperature being in therange of from about 250° C. to about 550° C. The preferred carbonburning temperature is in the range of from 300° C. to 500° C.

The oxygen concentration of the oxygen-containing gas can be controlledso as to provide the desired carbon burning temperature conditions. Theoxygen-containing gas is preferably air, which can be diluted with othergases, for instance, inert gases such as nitrogen, to control theconcentration of oxygen in the oxygen-containing gas. The carbon burncan be conducted within a combustion zone wherein is placed the spenthydroprocessing catalyst and into which is introduced theoxygen-containing gas. The time period for conducting the carbon burn isnot critical and is such as to provide the regenerated hydroprocessingcatalyst, having the desired carbon concentration, and it is generallyin the range of from about 0.1 hours to 48 hours, or longer.

It is generally desirable for the carbon content of the regeneratedhydroprocessing catalyst to be as low as is possible and, thus, thecarbon content of the regenerated hydroprocessing catalyst is typicallyless than 1 wt. %. However, it is usually preferred for the carboncontent of the regenerated hydroprocessing catalyst to be less than 0.75wt. %, and, more preferred, the carbon content is less than 0.5 wt. %.In the most preferred embodiment of the invention, the carbon content ofthe regenerated hydroprocessing catalyst is less than 0.3 wt. %. Apractical lower limit for the carbon content of the regeneratedhydroprocessing catalyst is greater than 0.01 wt. % or even greater than0.05 wt. %. Thus, for example, the carbon content of the regeneratedhydroprocessing catalyst may be in the range of from greater than 0.01wt. % to less than 1 wt. %.

In the inventive method, the regenerated hydroprocessing catalystundergoes a treatment with a chelating agent to provide a chelanttreated regenerated hydroprocessing catalyst that is subsequently dried.In this treatment step, a chelating agent is incorporated into theregenerated hydroprocessing catalyst by any suitable means or method,but it is preferred to contact, or wet, the regenerated hydroprocessingcatalyst with a chelating agent, which is preferably dissolved in aliquid carrier, in such a manner as to assure that the chelating agentis adequately incorporated into the regenerated hydroprocessingcatalyst.

The chelating agent, or chelant, suitable for use in the chelatingtreatment step of the inventive method includes those compounds that arecapable of forming complexes with the metal components, such as any ofthe Group VIB metals and Group VIII metals, as described above, of thehydroprocessing catalyst. It is important to the inventive method thatthe chelant have properties that provide for the formation of chelatecomplexes with the metals of the hydroprocessing catalyst in order topull the metals from the surface of its support material. The termschelant, chelating agent, and chelator are used herein to mean the samething and are considered to be a compound that functions as a ligand toform a chelate or chelate complex with a central metal ion.

The chelating agent is added to the regenerated hydroprocessing catalystin a liquid form preferably by use of a solution containing thechelating agent which complexes with the metal of the composition. Thecomplexes are, thus, in a liquid phase that provides for the weakeningof the bounds between the metal that is present throughout the supportmaterial.

Any chelant compound that suitably provides for the formation of metalchelate complexes as required by the inventive method described hereincan be used in the chelating treatment. Among these chelant compoundsare those chelating agents that contain at least one nitrogen atom thatcan serve as the electron donor atom for forming the complexes with themetals of the dried metal-incorporated support.

Examples of possible nitrogen atom containing chelating agents includethose compounds that can be classified as aminocarboxylic acids,polyamines, aminoalcohols, oximes, and polyethylene imines.

Examples of aminocarboxylic acids include ethylenediaminetetraaceticacid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA),diethylenetriaminepentaacetic acid (DTPA), and nitrilotriacetic acid(NTA).

Examples of polyamines include ethylenediamine, diethylenetriamine,triethylenetetramine, and triaminotriethylamine.

Examples of aminoalcohols include triethanolamine (TEA) andN-hydroxyethylethylenediamine.

The preferred chelating agent for use in the inventive method is anaminocarboxylic acid that can be represented by the following formula:

Wherein R₁, R₂, R₃, R₄ and R₅ are each independently selected fromalkyl, alkenyl, and allyl with up to 10 carbon atoms and which may besubstituted with one or more groups selected from carbonyl, carboxyl,ester, ether, amino, or amide; wherein R6 and R7 are each independentlyselected from an alkylene group with up to 10 carbon atoms; wherein n iseither 0 or 1; and wherein one or more of the R₁, R₂, R₃, R₄ and R₅ hasthe

Wherein, R₈ is an alkylene having from 1 to 4 carbon atoms; and whereinthe X is either hydrogen or another cation.

Preferred chelating agents include ethylenediaminetetraacetic acid(EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), anddiethylenetriaminepentaacetic acid (DTPA). The most preferred chelatingagent is DTPA.

Any suitable means or method can be used to contact the regeneratedhydroprocessing catalyst with the chelating agent or solution having aconcentration of chelating agent; provided, such means or methodprovides for the suitable incorporation or impregnation of the chelatingagent within the pores of the regenerated hydroprocessing catalyst.Examples of suitable methods of applying the chelating agent orchelating solution to the regenerated hydroprocessing catalyst caninclude dipping or spraying.

A preferred method for contacting the regenerated hydroprocessingcatalyst with the chelating agent or chelating solution is by anysuitable impregnation method known to those skilled in the art, forinstance, impregnation by incipient wetness whereby the amount or volumeof chelating solution added to the regenerated hydroprocessing catalystis such that the total volume of the added chelating solution is in anamount that may range upwardly to about the available pore volume of theregenerated hydroprocessing catalyst to be impregnated with thechelating solution.

The chelating solution can be a solution comprising the chelating agentand a solvent that suitably provides for the dissolution of thechelating agent. Possible solvents include water and alcohols, such as,methanol and ethanol, with water being the preferred solvent for thechelating agent.

The amount of chelating agent that is applied to the regeneratedhydroprocessing catalyst should be such as to provide for the desiredlevel of metal chelate complex formation as described herein; and,generally, the amount is such as to incorporate into the regeneratedhydroprocessing catalyst chelating agent in an amount in the range offrom about 0.005 moles chelant to about 1 mole chelant per mole ofactive metal, i.e., the Group VIB and Group VIII metals, as aredescribed above, that are in the regenerated hydroprocessing catalyst.

It is more preferred to add to the regenerated hydroprocessing catalystan amount of chelating agent that is in the range of from 0.01 to 0.5moles of added chelating agent per mole of hydrogenation metal. Mostpreferred, the amount of chelating agent added to the regeneratedhydroprocessing catalyst is in the range of from 0.05 to 0.1 moles ofadded chelant per mole of hydrogenation metal.

After the chelating agent is incorporated into the regeneratedhydroprocessing catalyst, the resulting chelant treated regeneratedhydroprocessing catalyst undergoes a drying step to remove at least aportion of the solvent in order to provide a dried chelant treatedregenerated hydroprocessing catalyst in which the polar additive may beincorporated.

The drying of the chelant treated regenerated hydroprocessing catalystis to remove at least a portion of the solvent of the chelating solutionfrom the chelant treated regenerated hydroprocessing catalyst whileleaving at least a portion, preferably a major portion of the chelatingagent on the chelant treated regenerated hydroprocessing catalyst. In apreferred embodiment of the invention, it is important for the driedchelant treated regenerated hydroprocessing catalyst to include thereinan amount or a concentration of chelant when a polar additive issubsequently incorporated into the dried chelant treated regeneratedhydroprocessing catalyst.

In the drying of the chelant treated regenerated hydroprocessingcatalyst it is desirable to remove as little of the chelant therefrom asis practical and, thus, more than about 50 weight percent of the chelantthat is incorporated into the chelant treated regeneratedhydroprocessing catalyst, based on the total weight of chelant containedin the chelant treated regenerated hydroprocessing catalyst, will remainin the resulting dried chelant treated regenerated hydroprocessingcatalyst.

It is preferred for the amount of chelant remaining on the dried chelanttreated regenerated hydroprocessing catalyst to exceed 75 weightpercent, and, most preferably, exceed 90 weight percent of the chelantoriginally added to the regenerated hydroprocessing catalyst andcontained in the chelant treated regenerated hydroprocessing catalyst toremain in the dried chelant treated regenerated hydroprocessing catalystwhen the polar additive is subsequently added. Thus, less than about 50weight percent of the chelant originally added to the regeneratedhydroprocessing catalyst in the chelation treatment thereof should beremoved from the chelant treated regenerated hydroprocessing catalystduring the drying step. Preferably, less than 25 weight percent and,most preferably, less than 10 weight percent, of the chelant containedin the chelant treated regenerated hydroprocessing catalyst is removedtherefrom.

The volatiles content of the dried chelant treated regeneratedhydroprocessing catalyst should be controlled so that it does not exceed25 wt. % LOI. LOI, or loss on ignition, is defined as the percentageweight loss of the material after its exposure to air at a temperatureof 482° C. for a period of two hours. LOI can be represented by thefollowing formula: (sample weight before exposure less sample weightafter exposure) multiplied by 100 and divided by (sample weight beforeexposure). It is preferred for the LOI of the dried chelant treatedregenerated hydroprocessing catalyst to be in the range of from 0.5 wt.% to 25 wt. % LOI, and, most preferred, from 1 wt. % to 20 wt. % LOI.

The drying can be conducted by any suitable method known to thoseskilled in the art. Typically, to dry the chelant treated regeneratedhydroprocessing catalyst, hot air or any other suitable gas, such asnitrogen and carbon dioxide, is passed over the chelant treatedregenerated hydroprocessing catalyst. The drying temperature should notexceed 200° C., and, can generally be in the range of from 90° C. to180° C. Preferably, the drying temperature is less than 175° C. and canrange from 100° C. to 175° C. The drying step is carefully controlled inorder to avoid either evaporating or converting the chelant or chelates.

The available pore volume of the pores of the dried chelant treatedregenerated hydroprocessing catalyst provided by drying of the chelanttreated regenerated hydroprocessing catalyst may be filled with thepolar additive of the invention. This is done by incorporating the polaradditive into the dried chelant treated regenerated hydroprocessingcatalyst to provide an additive impregnated composition by using anysuitable method or means to impregnate the dried chelant treatedregenerated hydroprocessing catalyst with the polar additive.

The preferred method of impregnation of the dried chelant treatedregenerated hydroprocessing catalyst with the polar additive may be anystandard well-known pore fill methodology whereby the pore volume isfilled by taking advantage of capillary action to draw the liquid intothe pores of the dried chelant treated regenerated hydroprocessingcatalyst. It is desirable to fill at least 75% of the available porevolume of the dried chelant treated regenerated hydroprocessing catalystwith the polar additive, and, preferably, at least 80% of the availablepore volume of the dried chelant treated regenerated hydroprocessingcatalyst is filled with the polar additive. Most preferably, at least90% of the available pore volume of the dried chelant treatedregenerated hydroprocessing catalyst is filled with the polar additive.

In addition to the dispersing of metal complexes by the polar additive,it is also thought that the presence of the polar additive in theadditive impregnated composition, when it is placed in catalytic serviceor when it undergoes an activation in order to use the composition incatalytic service, provides certain benefits that help give a much moreactive catalyst than those of the prior art.

The polar additive that may be used in the preparation of the inventivecomposition can be any suitable molecule that provides for the benefitsand has the characteristic molecular polarity or molecular dipole momentand other properties, if applicable, as are described herein, and as aredisclosed in co-pending U.S. application Ser. No. 12/407,479, filed Mar.19, 2009, (U.S. Publication No. US20100236988), which is incorporatedherein by reference.

Molecular polarity is understood in the art to be a result ofnon-uniform distribution of positive and negative charges of the atomsthat make up a molecule. The dipole moment of a molecule may beapproximated as the vector sum of the individual bond dipole moments,and it can be a calculated value.

One method of obtaining a calculated value for the dipole moment of amolecule, in general, includes determining by calculation the totalelectron density of the lowest energy conformation of the molecule byapplying and using gradient corrected density functional theory. Fromthe total electron density the corresponding electrostatic potential isderived and point charges are fitted to the corresponding nuclei. Withthe atomic positions and electrostatic point charges known, themolecular dipole moment can be calculated from a summation of theindividual atomic moments.

As the term is used in this description and in the claims, the “dipolemoment” of a given molecule is that as determined by calculation usingthe publicly available, under license, computer software program namedMaterials Studio, Revision 4.3.1, copyright 2008, Accerlys Software Inc.

Following below is a brief discussion of some of the technicalprinciples behind the computation method and application of theMaterials Studio computer software program for calculating moleculardipole moments.

The first step in the determination of the calculated value of thedipole moment of a molecule using the Materials Studio software involvesconstructing a molecular representation of the compound using thesketching tools within the visualizer module of Materials Studio. Thissketching process involves adding atoms to the sketcher window thatconstitute the compound and completing the bonds between these atoms tofulfill the recognized bonding connectivity that constitute thecompound. Using the clean icon within the Material Studio programautomatically orients the constructed compound into the correctorientation. For complex compounds, a conformational search is performedto ensure that the orientation used to calculate the molecular dipole isthe lowest energy conformation, i.e., its natural state.

The quantum mechanical code DMol3 (Delley, B. J. Chem. Phys., 92, 508(1990)) is utilized to calculate the molecular dipole moments from firstprinciples by applying density functional theory. Density functionaltheory begins with a theorem by Hohenberg and Kohn (Hohenberg, P.; Kohn,W. “Inhomogeneous electron gas”, Phys. Rev. B, 136, 864-871 (1964);Levy, M. “Universal variational functionals of electron densities,first-order density matrices, and natural spin-orbitals and solution ofthe v-representability problem”, Proc. Natl. Acad. Sci. U.S.A., 76,6062-6065 (1979)), which states that all ground-state properties arefunctions of the charge density ρ. Specifically, the total energy E_(t)may be written as:E _(t) [ρ]=T[ρ]+U[ρ]+E _(xc)[ρ]  Eq. 1where T [ρ] is the kinetic energy of a system of noninteractingparticles of density ρ, U [ρ] is the classical electrostatic energy dueto Coulombic interactions, and E_(xc) [ρ] includes all many-bodycontributions to the total energy, in particular the exchange andcorrelation energies.

As in other molecular orbital methods (Roothaan, C. C. J. “Newdevelopments in molecular orbital theory”, Rev. Mod. Phys., 23, 69-89(1951); Slater, J. C. “Statistical exchange-correlation in theself-consistent field”, Adv. Quantum Chem., 6, 1-92 (1972); Dewar, M. J.S. J. Mol. Struct., 100, 41 (1983)), the wavefunction is taken to be anantisymmetrized product (Slater determinant) of one-particle functions,that is, molecular orbitals:Ψ=A(n)|φ₁(1)φ₂(2) . . . φ_(n)(n)|  Eq. 2The molecular orbitals also must be orthonormal:

φ_(i)|φ_(j)

=δ_(ij)  Eq. 3The charge density summed over all molecular orbitals is given by thesimple sum:

$\begin{matrix}{{p(r)} = {\sum\limits_{i}\;{{\phi_{i}(r)}}^{2}}} & {{Eq}.\mspace{14mu} 4}\end{matrix}$where the sum goes over all occupied molecular orbitals φ_(i). Thedensity obtained from this expression is also known as the chargedensity. From the wavefunctions and the charge density the energycomponents from Eq. 1 can be written (in atomic units) as:

$\begin{matrix}{T = \langle {\sum\limits_{i}^{n}\;{\phi_{i}{\frac{- \nabla^{2}}{2}}\phi_{i}}} \rangle} & {{Eq}.\mspace{14mu} 5}\end{matrix}$

In Eq. 6, Z α refers to the charge on nucleus α of an N-atom system.Further, in Eq. 6, the term ρ(r₁)V_(N), represents the electron-nucleusattraction, the term ρ(r₁)V_(e)(r₁)/2, represents the electron-electronrepulsion, and the term, V_(NN), represents the nucleus-nucleusrepulsion.

$\begin{matrix}\begin{matrix}{U = {{\sum\limits_{i}^{n}\;{\sum\limits_{\alpha}^{N}\;\langle {{\phi_{i}(r)}{\frac{- Z}{R_{\alpha} - r}}{\phi_{i}(r)}} \rangle}} +}} \\{{\frac{1}{2}{\sum\limits_{i}\;{\sum\limits_{j}\;\langle {{\phi_{i}( r_{1} )}{\phi_{j}( r_{2} )}\frac{1}{r_{1} - r_{2}}{\phi_{i}( r_{1} )}{\phi_{j}( r_{2} )}} \rangle}}} + {\sum\limits_{\alpha}^{N}\;{\sum\limits_{\beta < \alpha}\;\frac{Z_{\alpha}Z_{\beta}}{{R_{\alpha} - R_{\beta}}}}}} \\{= {{- {\sum\limits_{\alpha}^{N}\;\langle {{p( r_{1} )}\frac{Z_{\alpha}}{{R_{\alpha} - r_{1}}}} \rangle}} + {\frac{1}{2}\langle {{p( r_{1} )}{p( r_{2} )}\frac{1}{{r_{1} - r_{2}}}} \rangle} +}} \\{\sum\limits_{\alpha}^{N}\;{\sum\limits_{\beta < \alpha}\;\frac{Z_{\alpha}Z_{\beta}}{{R_{\alpha} - R_{\beta}}}}} \\{\equiv {\langle {{- {p( r_{1} )}}V_{N}} \rangle + \langle {{p( r_{1} )}\frac{V_{e}( r_{1} )}{2}} \rangle + V_{NN}}}\end{matrix} & {{Eq}.\mspace{14mu} 6}\end{matrix}$

The term, E_(xc)[ρ] in Eq. 1, the exchange-correlation energy, requiressome approximation for this method to be computationally tractable. Asimple and surprisingly good approximation is the local densityapproximation, which is based on the known exchange-correlation energyof the uniform electron gas. (Hedin, L.; Lundqvist, B. I. “Explicitlocal exchange correlation potentials”, J. Phys. C, 4, 2064-2083 (1971);Ceperley, D. M.; Alder, B. J. “Ground state of the electron gas by astochastic method”, Phys. Rev. Lett., 45, 566-569 (1980)). The localdensity approximation assumes that the charge density varies slowly onan atomic scale (i.e., each region of a molecule actually looks like auniform electron gas). The total exchange-correlation energy can beobtained by integrating the uniform electron gas result:ε_(xc)[ρ]≅∫ρ(r)ε_(xc)[ρ(r)]dr  Eq. 7

where E_(xc)[ρ] is the exchange-correlation energy per particle in auniform electron gas and ρ is the number of particles. In this work thegradient corrected exchange-correlation functional PW91 is used (Perdew,J. P.; Wang, Y. Phys. Rev. B, 45, 13244 (1992)).

With all the components derived to describe the total energy of anymolecular system within the density functional formalism, the dipolemoment can be calculated from a summation of the individual electronicand nuclear dipole moment vectors which are displayed at the end of theDMol3 output file.

References herein to the polar additive are understood to mean amolecule that has polarity and having a dipole moment, as calculated bythe aforementioned Materials Studio software or other known method thatwill provide substantially the same calculated value for the dipolemoment of a molecule as the Materials Studio software will provide,which exceeds the dipole moment of the hydrocarbon oil that is used inthe inventive composition.

The dipole moment of the polar additive should be at least or exceed0.45. However, it is preferred for the polar additive to have acharacteristic dipole moment that is at least or exceeds 0.5, and, morepreferred, the dipole moment of the polar additive should be at least orexceed 0.6. A typical upper limit to the dipole moment of the polaradditive is up to about 5, and, thus, the dipole moment of the polaradditive may be, for example, in the range of from 0.45 to 5. It ispreferred for the dipole moment of the polar additive to be in the rangeof from 0.5 to 4.5, and, more preferred, the dipole moment is to be inthe range of from 0.6 to 4.

As alluded to above, it is theorized that the polarity of the polaradditive is significant to the invention; because, the polarity isrequired for the interaction with the surface of the support materialand active metal components of the support material of the inventivecomposition. It is by these interactions that physical and chemicalbonds with the active phases of the inventive composition are formed.

A particularly desirable attribute of the polar additive is for it to bea heterocompound. A heterocompound is considered herein to be a moleculethat includes atoms in addition to carbon and hydrogen. These additionalatoms can include, for example, nitrogen or oxygen, or both. It isdesirable for the group of hetercompounds to exclude thoseheterocompounds that include sulfur, and, in all cases, the polaradditive does not include paraffin and olefin compounds, i.e. compoundsthat contain only carbon and hydrogen atoms. Considering the exclusionof sulfur-containing compounds from the definition of the group ofheterocompounds, it can further be desirable for the oil and additiveimpregnated composition, before its treatment with hydrogen and sulfur,to exclude the material presence of a sulfur-containing compound.

Specific polar compounds that may be suitable for use as the polaradditive of the invention are presented in the following Table 1, whichalso includes their calculated dipole moments.

TABLE 1 Polar Compounds and Their Calculated Dipole Moments BoilingCalc. Point Dipole Compound Formula Class (° C.) Moment 2,4-pentanedioneC₅H₈O₂ Diketone 140 1.59 Triethylphosphate C₆H₁₅O₄P Phosphate 215-2163.25 Triethylphosphite C₆H₁₅O₃P Phosphite 156 0.64 1-pentanol C₅H₁₂OAlcohol 138 1.85 Guanidine CH₅N₃ Imine n/a 3.8 Alanine C₃H₇NO₂ Aminoacid n/a 2.16 Glycine C₂H₅NO₂ Amino acid n/a 5.81 EthyleenediamineC₂H₈N₂ Diamine 116 2.46 Monoethanolamine C₂H₇NO Alcohol-amine 170 3.42Tetramethylurea C₅H₁₂N₂O Diamine 174-178 3.44 Acetonitrile C₂H₃N Nitrile 82 3.87 n-methylpyrrolidone C₅H₉NO Cyclic-amide 202 3.92 GlucoseC₆H₁₂O₆ sugar n/a 4.38 Sucrose C₁₂H₂₂O₁₁ sugar n/a 7.45 OctylamineC₈H₁₉N Amine 175-176 1.36 Phenylboromic acid C₆H₇BO₂ Boric acid n/a 5.86n-ethylcarbazole C₁₄H₁₃N Carbazole n/a 1.93 Acetophenone C₈H₈O ketone202 3.15 Diethyleneglycol C₄H₁₀O₃ Alcohol 244-245 2.76 DibenzofuranC₁₂H₈O Oxygen heterocycle 285 0.78 Dimethylformamide C₃H₇NO Amide 1534.02 Citric acid C₆H₈O₇ Carboxylic acid 175 3.37Ethylenediaminetetraacetic acid C₁₀H₁₆N₂O₈ Polyamino carboxylic n/a 3.99acid Nitriltriacetic acid C₆H₉NO₆ Polyamino carboxylic n/a 1.58 acid

A preferred characteristic of the polar additive is for its boilingtemperature to be in the range of from 50° C. to 275° C. Morepreferably, the boiling temperature of the polar additive is to be inthe range of from 60° C. to 250° C., and, most preferably, it is in therange of from 80° C. to 225° C.

The most desirable compounds for use as the polar additive of theinvention are those selected from the group of amide compounds, whichincludes dimethylformamide.

The additive impregnated composition of the invention may be treated,either ex situ or in situ, with hydrogen and with a sulfur compound,and, indeed, it is one of the beneficial features of the invention thatit permits the shipping and delivery of a non-sulfurized composition toa reactor in which it can be activated, in situ, by a hydrogen treatmentstep followed by a sulfurization step. In the activation of the additiveimpregnated composition it first can undergo a hydrogen treatment thatis then followed with treatment with a sulfur compound.

The hydrogen treatment includes exposing the additive impregnatedcomposition to a gaseous atmosphere containing hydrogen at a temperatureranging upwardly to 250° C. Preferably, the additive impregnatedcomposition is exposed to the hydrogen gas at a hydrogen treatmenttemperature in the range of from 100° C. to 225° C., and, mostpreferably, the hydrogen treatment temperature is in the range of from125° C. to 200° C.

The partial pressure of the hydrogen of the gaseous atmosphere used inthe hydrogen treatment step generally can be in the range of from 1 barto 70 bar, preferably, from 1.5 bar to 55 bar, and, most preferably,from 2 bar to 35 bar. The additive impregnated composition is contactedwith the gaseous atmosphere at the aforementioned temperature andpressure conditions for a hydrogen treatment time period in the range offrom 0.1 hours to 100 hours, and, preferably, the hydrogen treatmenttime period is from 1 hour to 50 hours, and most preferably, from 2hours to 30 hours.

Sulfiding of the additive impregnated composition after it has beentreated with hydrogen can be done using any conventional method known tothose skilled in the art. Thus, the hydrogen treated additiveimpregnated composition can be contacted with a sulfur-containingcompound, which can be hydrogen sulfide or a compound that isdecomposable into hydrogen sulfide, under the contacting conditions ofthe invention. Examples of such decomposable compounds includemercaptans, CS₂, thiophenes, dimethyl sulfide (DMS), and dimethyldisulfide (DMDS). Also, preferably, the sulfiding is accomplished bycontacting the hydrogen treated composition, under suitablesulfurization treatment conditions, with a hydrocarbon feedstock thatcontains a concentration of a sulfur compound. The sulfur compound ofthe hydrocarbon feedstock can be an organic sulfur compound,particularly, one which is typically contained in petroleum distillatesthat are processed by hydrodesulfurization methods.

Suitable sulfurization treatment conditions are those which provide forthe conversion of the active metal components of the hydrogen treatedhydrocarbon oil and polar additive impregnated composition to theirsulfided form. Typically, the sulfiding temperature at which thehydrogen treated hydrocarbon oil and polar additive impregnatedcomposition is contacted with the sulfur compound is in the range offrom 150° C. to 450° C., preferably, from 175° C. to 425° C., and, mostpreferably, from 200° C. to 400° C.

When using a hydrocarbon feedstock that is to be hydrotreated using thecatalyst composition of the invention to sulfide the hydrogen treatedcomposition, the sulfurization conditions can be the same as the processconditions under which the hydrotreating is performed. The sulfidingpressure at which the hydrogen treated additive impregnated compositionis sulfided generally can be in the range of from 1 bar to 70 bar,preferably, from 1.5 bar to 55 bar, and, most preferably, from 2 bar to35 bar.

One of the benefits provided by the additive impregnated composition ofthe invention is that it can be utilized in a reactor system that isstarted up using a so-called delayed feed introduction procedure. In thedelayed feed introduction procedure, the reactor system, which includesa reactor vessel containing the additive impregnated composition, firstundergoes a heating step to raise the temperature of the reactor and theadditive impregnated composition contained therein in preparation forthe introduction of a sulfiding agent or heated hydrocarbon feedstockfor processing. This heating step includes introducing into the reactorthe hydrogen-containing gas at the aforementioned hydrogen treatmentconditions. After the hydrogen treatment of the additive impregnatedcomposition, it is thereafter treated with a sulfur compound in themanner as earlier described herein.

It has been found that the additive impregnated composition, afterundergoing the hydrogen treatment followed by treatment with a sulfurcompound, exhibits a greater catalytic hydrotreating activity of adistillate feedstock than do other similar, but non-impregnatedcompositions.

It is recognized that the additive impregnated composition of theinvention, after its treatment with hydrogen and sulfur, is a highlyeffective catalyst for use in the hydrotreating of hydrocarbonfeedstocks. This catalyst is particularly useful in applicationsinvolving the hydrodesulfurization or hydrodenitrogenation ofhydrocarbon feedstocks, and, especially, it has been found to be anexcellent catalyst for use in the hydrodesulfurization of distillatefeedstocks, in particular, diesel, to make an ultra-low sulfurdistillate product having a sulfur concentration of less than 15 ppmw,preferably, less than 10 ppmw, and, most preferably, less than 8 ppmw.

In the hydrotreating applications, the additive impregnated composition,preferably used in a delayed feed introduction procedure or otherwisetreated with hydrogen and sulfur, as described above, is contacted undersuitable hydrodesulfurization conditions with a hydrocarbon feedstockthat typically has a concentration of sulfur. The more typical andpreferred hydrocarbon feedstock is a petroleum middle distillate cuthaving a boiling temperature at atmospheric pressure in the range offrom 140° C. to 410° C. These temperatures are approximate initial andboiling temperatures of the middle distillate. Examples of refinerystreams intended to be included within the meaning of middle distillateinclude straight run distillate fuels boiling in the referenced boilingrange, such as, kerosene, jet fuel, light diesel oil, heating oil, heavydiesel oil, and the cracked distillates, such as FCC cycle oil, cokergas oil, and hydrocracker distillates. The preferred feedstock of theinventive distillate hydrodesulfurization process is a middle distillateboiling in the diesel boiling range of from about 140° C. to 400° C.

The sulfur concentration of the middle distillate feedstock can be ahigh concentration, for instance, being in the range upwardly to about 2weight percent of the distillate feedstock based on the weight ofelemental sulfur and the total weight of the distillate feedstockinclusive of the sulfur compounds. Typically, however, the distillatefeedstock of the inventive process has a sulfur concentration in therange of from 0.01 wt. % (100 ppmw) to 1.8 wt. % (18,000). But, moretypically, the sulfur concentration is in the range of from 0.1 wt. %(1000 ppmw) to 1.6 wt. % (16,000 ppmw), and, most typically, from 0.18wt. % (1800 ppmw) to 1.1 wt. % (11,000 ppmw). It is understood that thereferences herein to the sulfur content of the distillate feedstock areto those compounds that are normally found in a distillate feedstock orin the hydrodesulfurized distillate product and are chemical compoundsthat contain a sulfur atom and which generally include organosulfurcompounds.

The additive impregnated composition of the invention may be employed asa part of any suitable reactor system that provides for contacting it orits derivatives with the distillate feedstock under suitablehydrodesulfurization conditions that may include the presence ofhydrogen and an elevated total pressure and temperature. Such suitablereaction systems can include fixed catalyst bed systems, ebullatingcatalyst bed systems, slurried catalyst systems, and fluidized catalystbed systems. The preferred reactor system is that which includes a fixedbed of the inventive catalyst contained within a reactor vessel equippedwith a reactor feed inlet means, such as a feed nozzle, for introducingthe distillate feedstock into the reactor vessel, and a reactor effluentoutlet means, such as an effluent outlet nozzle, for withdrawing thereactor effluent or the treated hydrocarbon product or the ultra-lowsulfur distillate product from the reactor vessel.

The hydrodesulfurization process generally operates at ahydrodesulfurization reaction pressure in the range of from 689.5 kPa(100 psig) to 13,789 kPa (2000 psig), preferably from 1896 kPa (275psig) to 10,342 kPa (1500 psig), and, more preferably, from 2068.5 kPa(300 psig) to 8619 kPa (1250 psig).

The hydrodesulfurization reaction temperature is generally in the rangeof from 200° C. (392° F.) to 420° C. (788° F.), preferably, from 260° C.(500° F.) to 400° C. (752° F.), and, most preferably, from 320° C. (608°F.) to 380° C. (716° F.). It is recognized that one of the unexpectedfeatures of the use of the inventive additive impregnated composition ofthe invention is that it has a significantly higher catalytic activitythan certain other alternative catalyst compositions, and, thus, itwill, in general, provide for comparatively lower required processtemperatures for a given amount of hydrotreatment of a feedstock.

The flow rate at which the distillate feedstock is charged to thereaction zone of the inventive process is generally such as to provide aliquid hourly space velocity (LHSV) in the range of from 0.01 hr⁻¹ to 10hr⁻¹. The term “liquid hourly space velocity”, as used herein, means thenumerical ratio of the rate at which the distillate feedstock is chargedto the reaction zone of the inventive process in volume per hour dividedby the volume of catalyst contained in the reaction zone to which thedistillate feedstock is charged. The preferred LHSV is in the range offrom 0.05 hr⁻¹ to 5 hr⁻¹, more preferably, from 0.1 hr⁻¹ to 3 hr⁻¹. and,most preferably, from 0.2 hr⁻¹ to 2 hr⁻¹.

It is preferred to charge hydrogen along with the distillate feedstockto the reaction zone of the inventive process. In this instance, thehydrogen is sometimes referred to as hydrogen treat gas. The hydrogentreat gas rate is the amount of hydrogen relative to the amount ofdistillate feedstock charged to the reaction zone and generally is inthe range upwardly to 1781 m³/m³ (10,000 SCF/bbl). It is preferred forthe treat gas rate to be in the range of from 89 m³/m³ (500 SCF/bbl) to1781 m³/m³ (10,000 SCF/bbl), more preferably, from 178 m³/m³ (1,000SCF/bbl) to 1602 m³/m³ (9,000 SCF/bbl), and, most preferably, from 356m³/m³ (2,000 SCF/bbl) to 1425 m³/m³ (8,000 SCF/bbl).

The desulfurized distillate product yielded from the process of theinvention has a low or reduced sulfur concentration relative to thedistillate feedstock. A particularly advantageous aspect of theinventive process is that it is capable of providing a deeplydesulfurized diesel product or an ultra-low sulfur diesel product. Asalready noted herein, the low sulfur distillate product can have asulfur concentration that is less than 50 ppmw or any of the other notedsulfur concentrations as described elsewhere herein (e.g., less than 15ppmw, or less than 10 ppmw, or less than 8 ppmw).

The following Examples are presented to illustrate the invention, butthey should not be construed as limiting the scope of the invention.

EXAMPLE 1

This Example describes the regeneration and revitalization by chelationtreatment of a commercially available hydroprocessing catalyst(Reference Catalyst) that has become spent by it use in the treatment ofa hydrocarbon feedstock. The regenerated and revitalized product isidentified as Catalyst A.

The alumina support particle used in the compositions of Examples 1-4was made by mixing alumina and water to form a mixture that was extrudedinto 1.3 mm Trilobe extrudates. The shaped support extrudates were driedand calcined using standard drying and calcination techniques so as toprovide an alumina carrier for loading the active metals and additivecomponents of the compositions. The properties of the shaped aluminasupport are presented in Table 2 below.

TABLE 2 Properties of Shaped Support Property Value Shape 1.3 mm TrilobeSurface area (m2/g) 245 to 320 Mean pore diameter (Ang.)  80 to 100 Porevolume greater than 350 Ang. (%) Less than 5 Water pore volume (cc/g)0.74 to 0.90 Nickel (wt. %) 1.0

An amount of the shaped support described above, was impregnated with anaqueous impregnation solution (metal-containing solution) comprising anickel component, a molybdenum component, and a phosphorous component.The aqueous impregnation solution was prepared by dissolving nickeloxide (NiO), molybdenum trioxide (MoO₃) and phosphoric acid inde-ionized water with heating and stirring. A volume of the aqueousimpregnation solution was used to fill the pores of the extrudate so asto load it with 4.5 wt % cobalt, 1.5% nickel, 16.5 wt % molybdenum, and3.1 wt % phosphorous, with the weight percents being on a dry basis andthe metals as element. The impregnated shaped particles (extrudates)were allowed to age for two hours, and, then dried in air at a dryingtemperature of 100° C. to reduce the volatiles content to 7.3 wt %. Thecatalyst precursor was then presulfurized, ex situ, followed by its usein the hydrotreatment of a distillate feedstock under commercialprocessing conditions until spent and then regenerated by the burning ofthe deposited coke to thereby provide Composition A. Composition A wasnot treated with and did not contain a chelating agent or a polaradditive.

EXAMPLE 2

This Example 2 describes the preparation of comparative Composition Bthat has not been subject to a chelating treatment but included a polaradditive.

Composition A was impregnated with the polar additive dimethylformamide(DMF) to fill substantially all of the free pore volume to provideComposition B.

EXAMPLE 3

This Example 3 describes the preparation of comparative Composition Cthat has been treated with a chelating agent but does not include apolar additive.

Composition A was impregnated with a solution comprising the chelatingagent diethylenetriaminepentaacetic acid (DTPA). This solution wasprepared as follows: 2726 weight parts of deionized water was mixed with283 weight parts DTPA powder (99% concentration, BASF, Trilon C Powder).To this mixture, 105 weight parts ammonium hydroxide at 29% NH₃concentration was added. Heat was used as needed to dissolve thecomponents of the solution. The final solution had a specific gravity ofapproximately 1.04 g/cc and solution concentrations of 9% DTPA and 0.98%NH₃. In the impregnation of Composition A with the solution comprisingthe chelating agent, a substantial proportion of the free pore volumewas filled with the solution.

Following the pore volume impregnation of Composition A with thesolution of chelating agent, the chelant treated Composition A (chelanttreated metal-incorporated support) was dried in air at a temperature inthe range of from 120 to 130° C. for 4 hours to yield Composition C.

EXAMPLE 4

This Example 4 describes the preparation of Composition D, which is oneembodiment of the inventive composition, containing hydrogenation metalcomponents and which has been treated with a chelating agent and filledwith a polar additive.

Composition A was impregnated with a solution comprising the chelatingagent diethylenetriaminepentaacetic acid (DTPA). This solution wasprepared as follows: 2726 weight parts of deionized water was mixed with283 weight parts DTPA powder (99% concentration, BASF, Trilon C Powder).To this mixture 105 weight parts ammonium hydroxide at 29% NH₃concentration was added. Heat was used as needed to dissolve thecomponents of the solution. The final solution had a specific gravity ofapproximately 1.04 g/cc and solution concentrations of 9% DTPA and 0.98%NH₃. In the impregnation of Composition A with the solution comprisingthe chelating agent, a substantial proportion of the free pore volumewas filled with the solution.

Following the pore volume impregnation of Composition A with thesolution of chelating agent, the chelant treated Composition A (chelanttreated metal-incorporated support) was dried in air at a temperature inthe range of from 120 to 130° C. for 4 hours to eliminate excessmoisture and reduce the volatiles content thereof to a target LOI and tofree up pore volume that could subsequently be filled with a polaradditive. The dried chelant treated Composition A (dried chelant treatedmetal-incorporated support) was then filled by pore volume impregnationwith the polar additive dimethylformamide (DMF) to at least a 90% porevolume fill to give the inventive Composition D (additive impregnatedcomposition).

EXAMPLE 5

This Example 5 describes the procedure for testing the catalyticperformance of the compositions of Examples 2-4, and it presents theperformance results from their use in the hydrotreating of a gas oilfeedstock (activity testing).

Trickle flow micro-reactors were used to test the hydrodesulfurizationactivity of Compositions B, C and D. A 50 cc volume, based on compactedbulk density of whole pellets, of each composition was used in thetesting. The reactors were packed with extrudates of each composition,which were diluted with 80-60 mesh SiC in the volumetriccomposition-to-diluent ratio of 1:2.8. The compositions were conditionedand sulfided using a delayed-feed introduction procedure whereby thecomposition was first heated up and conditioned by contacting it withpure hydrogen at the operating pressure and at a temperature in therange of from 149° C. (300° F.) to 204° C. (400° F.) for a time periodof about 12 hours. Following this hydrogen treatment, the compositionwas sulfided using a liquid hydrocarbon containing TNPS to provide asulfur content of 2.5%.

The activity of the compositions were tested by charging the reactorwith a blended feedstock of a diesel boiling range having thedistillation properties (per ASTM test D 2287) that are presented inTable 3. The feedstock had a sulfur content of 1.71 wt. %, and it wascharged to the reactor, which was operated at a pressure of 600 psig, ata rate so as to provide a liquid hourly space velocity (LHSV) of 1.0hr⁻¹. The hydrogen gas rate charged to the reactor was 1200 scf H₂/bbl.The weight average bed temperature (WABT) was adjusted to provide atreated product having a sulfur content that was 10 ppmw.

TABLE 3 Distillation (D-2287) of Diesel Feedstock With 1.71 wt. % Sulfur% ° F. IBP 272  5 387 10 440 20 489 30 520 40 539 50 558 60 578 70 60080 624 90 652 95 674 EP 776

FIG. 1 presents the results of the testing with activity determined asthe WABT required to achieve targeted 10 ppm sulfur content in theproduct. It can be observed from the presented plots that the inventiveComposition D exhibits a higher activity (a lower WABT for the given HDSlevel) than the comparative Compositions B and C. Composition D provided10 ppm total sulfur in the product at c.a. 665° F. whereas CompositionsB and C showed a 10 ppm total sulfur in the product at c.a. 685° F.Composition D provides a significant temperature advantage of at least a11.1° C. (20° F.) over either Composition B or Composition C.

That which is claimed is:
 1. A method for restoring catalytic activityto a hydroprocessing catalyst comprising a Group VIB metal component, aGroup VIII metal component, or both metal compounds on a supportmaterial, wherein said hydroprocessing catalyst has become spent as aresult of its use so as to provide a spent hydroprocessing catalysthaving a carbon content above 0.5 wt. %, and to provide an additiveimpregnated composition, wherein said method comprises: regeneratingsaid spent hydroprocessing catalyst to remove at least a portion of thecarbon therefrom to provide a regenerated hydroprocessing catalyst;treating said regenerated hydroprocessing catalyst with a chelatingagent capable of forming a complex with a metal component of saidhydroprocessing catalyst and selected from the group consisting ofcompounds consisting of aminocarboxylic acids, polyamines, aminoalcohols, oximes, and polyethylene imines, by incorporating saidchelating agent into said regenerated hydroprocessing catalyst toprovide a chelant treated regenerated hydroprocessing catalyst; dryingsaid chelant treated regenerated hydroprocessing catalyst to provide adried chelant treated regenerated hydroprocessing catalyst having avolatiles content in the range of from 0.5 to 25 wt % LOI; andincorporating a polar additive comprising a heterocompound havingpolarity and a dipole moment of at least 0.45 and selected from a groupconsisting of amide compounds into said dried chelant treatedregenerated hydroprocessing catalyst to provide said additiveimpregnated composition.
 2. A method as recited in claim 1, wherein saidstep of drying said chelant treated regenerated hydroprocessing catalystis conducted at a drying temperature not to exceed 400° C.
 3. A methodas recited in claim 2, wherein at least 75% of the available pore volumeof said dried chelant treated regenerated hydroprocessing catalyst isfilled with said polar additive.
 4. A composition made by the method ofclaim
 3. 5. A method as recited in claim 3, further comprising: hydrogentreating said additive impregnated composition by exposing it to agaseous atmosphere containing hydrogen at a temperature ranging upwardlyto 250° C. to provide an hydrogen treated additive impregnatedcomposition.
 6. A method as recited in claim 3, further comprising:sulfiding said hydrogen treated additive impregnated composition bycontacting it with a sulfur-containing compound under suitablesulfurization treatment conditions.
 7. A method as recited in claim 3,further comprising: sulfiding said additive impregnated composition bycontacting it with a sulfur-containing compound under suitablesulfurization treatment conditions.
 8. A method as recited in claim 3,wherein said polar additive has a boiling temperature within the rangeof from 50° C. to 275° C.
 9. A method as recited in claim 8, whereinsaid polar additive has a dipole moment exceeding 0.5.
 10. A method asrecited in claim 8, wherein said polar additive has a dipole momentexceeding 0.6.
 11. A method as recited in claim 10, wherein said polaradditive has a boiling temperature in the range of from 50° C. to 275°C.
 12. A method as recited in claim 10, wherein said polar additive hasa boiling temperature in the range of from 80° C. to 225° C.
 13. Amethod as recited in claim 12, wherein said Group VIII metal componentis either nickel or cobalt present in said hydroprocessing catalyst inan amount in the range of from 0.1 to 6 weight percent, based on themetal as an element and the total weight of the hydroprocessingcatalyst, and said Group VIB metal component is either molybdenum orchromium present in said hydroprocessing catalyst in an amount in therange of from 5 to 25 weight percent, based on the metal as an elementand the total weight of the hydroprocessing catalyst, and said supportmaterial is an alumina.
 14. A method as recited in claim 12, whereinsaid chelating agent is selected from the group consisting ofethylenediaminetetraacetic acid (EDTA), hydroxyethlenediaminetriaceticacid (HEDTA), and diethylenetriaminepentaacetic acid (DTPA).
 15. Amethod as recited in claim 12, wherein said polar additive isdimethylformamide.
 16. A method as recited in claim 12, wherein saidchelating agent is diethylenetriaminepentaacetic acid (DTPA).
 17. Amethod as recited in claim 12, wherein said spent hydroprocessingcatalyst has a carbon content in the range of from 1 weight percent to25 weight percent, and said regenerated hydroprocessing catalyst has acarbon content of less than 0.75 wt. %.
 18. A method as recited in claim12, wherein said regenerated hydroprocessing catalyst has a carboncontent of less than 0.5 wt. %.
 19. A method as recited in claim 12,wherein an amount of said chelating agent incorporated into saidregenerated hydroprocessing catalyst is in the range of from 0.005 moleschelant to 1 mole chelant per mole of active Group VIB and Group VIIImetal.
 20. A composition made by the method of claim
 2. 21. Acomposition made by the method of claim 1.